1. Technical Field of the Invention
The present invention relates to packet data communication and, in particular, to the communication of packet data, such as an Internet Protocol (IP) packet, toward a mobile station roaming within an incompatible mobile network.
2. Description of Related Art
Developments and improvements in mobile telecommunications networks have enable mobile subscribers to communicate data, other than mere voice data, over a serving mobile telecommunications network. With a wide proliferation of Internet and e-mail applications, mobile subscribers are able to access their e-mail messages or even browse or "surf" the Internet via their associated mobile stations. Accordingly, a mobile station may function as data terminal equipment (DTE) in providing Internet access or packet communication to an associated mobile subscriber.
Unlike voice communication, packet communication towards mobile stations has not yet been fully standardized. As a result, a number of different standards, protocols, and/or schemes are available to provide packet communication with a mobile station. Such differences in standards are especially true with respect to maintaining a particular mobile station's current location and its registration status. A method and/or scheme for maintaining data associated with a particular mobile station and its location is referred to as "mobility management" and is needed for enabling a mobile station to freely travel or roam within a particular network.
As an illustration, one such standard requires a separate mobility management infrastructure and routing scheme for effectuating packet communication with a mobile station. Such a standard only utilizes a serving mobile switching center (MSC) and base station (BS) associated with an existing mobile telecommunications network for establishing an over-the-air interface with the mobile station located within a particular geographic area. Accordingly, serving mobile telecommunications nodes and devices, such as an MSC and BS, are only utilized for the very last leg of the packet communication link with a mobile station. Such a standard is referred to as a Mobile IP Method (MIM) where a mobile station is assigned with a packet data network independent Internet Protocol (IP) address. The mobility management (MM) for keeping track of the current location of a mobile station and for effectuating packet communication therewith are further performed by separate packet data communications nodes, such as a home agent (HA) and foreign agent (FA).
Another standard for communicating packet data utilizes existing mobile telecommunications nodes and devices for effectuating mobility management associated with a particular mobile station. A home location register (HLR) is utilized within a conventional mobile telecommunications network for maintaining subscription data and for keeping track of a particular mobile station having a subscription therewith. Accordingly, each time a mobile station travels into a geographic area being served by a new MSC, the new MSC communicates with the associated HLR to inform the HLR of the mobile station's new location and to retrieve requisite subscriber data associated with the newly registering mobile station. When an incoming voice call connection is requested toward the mobile station, the serving mobile telecommunications network interrogates the HLR to retrieve the location data previously provided by the serving MSC. Such data are then utilized by a serving Gateway Mobile Switching Center (GMSC), for example, to reroute the received voice call connection to the serving MSC.
Similarly for packet data communication, the existing HLR-MSC location update mechanism and data as described above are also utilized by the packet switching network to locate and to reroute packet data to the destination mobile station. Accordingly, in a manner similar to the HLR interrogation performed by the serving mobile telecommunications network for routing incoming voice calls, the packet data network similarly communicates with the HLR to identify the MSC currently serving the destination mobile station. A gateway packet mobile switching center (GPMSC), for example, then reroutes packets to a Visited Packet Mobile Switching Center (VPMSC) associated with the identified MSC. The serving MSC and BS associated with the VPMSC then establish a radio link with the destination mobile station to effectuate data packet communication in a conventional manner. Such a standard is commonly referred to as a traditional cellular mobility method. One example of a packet data communications network utilizing such a standard is a Personal Digital Cellular Mobility Method network (PDCMM or more commonly known as PMM network).
Even though there are different types of data packet communications standards, as long as a mobile station roams within a mobile telecommunications network utilizing a compatible packet communications standard, a corresponding mobility management scheme communicates with appropriate devices and nodes to enable the mobile station to access packet communication. However, when a mobile station belonging to a first mobile telecommunications network utilizing a first packet communications standard roams into a second mobile telecommunications network utilizing a second packet communications standard, there is currently no mechanism for enabling the mobile station to access packet data communication while visiting the incompatible second packet telecommunications network. As a result, for packet communication, a mobile station is currently restricted to roam within a compatible mobile telecommunications network.
Accordingly, there is a need for a mechanism to enable a mobile station to roam from a first mobile telecommunications network utilizing a first packet communications standard to a second mobile telecommunications network utilizing a second packet communications standard.